In the existing technology, small changes in physical quantities such as length, temperature, refractive index, pressure and so on are usually measured through the laser phase interferometry. A Mach-Zehnder interferometer based sensor is a common sensor making use of the laser phase interferometry for measuring. The measuring principle comprises dividing the laser beam output from laser into two beams which respectively come into the two arms of the interferometer; uniting the two beams having passed different transmission paths to form interference; detecting the phase difference of the two beams by a detector; and determining the measured physical quantity. Because the amounts of optical paths of the two arms can be affected by external conditions such as temperature, pressure and so on, the Mach-Zehnder interferometer can finish the measurement of physical quantities such as strain and temperature, and is the important physical basis of many sensors. But such sensor detects the phase difference of two beams of laser, the detection precision and sensitivity is still limited and it needs to provide a new type sensor of high precision and high sensitivity.